linux-kernel - Re: [RFT][PATCH v2 1/9] vfio: Make vfio_unpin

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Message-ID: <YsUxurAoglm7GmZP@infradead.org>
Date:   Tue, 5 Jul 2022 23:54:50 -0700
From:   Christoph Hellwig <hch@...radead.org>
To:     Nicolin Chen <nicolinc@...dia.com>
Cc:     kwankhede@...dia.com, corbet@....net, hca@...ux.ibm.com,
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Subject: Re: [RFT][PATCH v2 1/9] vfio: Make vfio_unpin_pages() return void

> +void vfio_unpin_pages(struct vfio_device *device, unsigned long *user_pfn,
> +		      int npage)
>  {
>  	struct vfio_container *container;
>  	struct vfio_iommu_driver *driver;
> -	int ret;
>  
> -	if (!user_pfn || !npage || !vfio_assert_device_open(device))
> -		return -EINVAL;
> +	if (WARN_ON_ONCE(!user_pfn || !npage || !vfio_assert_device_open(device)))

This adds an overly long line.  Note that I think in general it is
better to have an individual WARN_ON per condition anyway, as that
allows to directly pinpoint what went wrong when it triggers.

> +	if (WARN_ON_ONCE(unlikely(!driver || !driver->ops->unpin_pages)))
> +		return;

I'd just skip this check an let it crash.  If someone calls unpin
on something totally random that wasn't even pinned we don't need to
handle that gracefully.

Otherwise looks good:

Reviewed-by: Christoph Hellwig <hch@....de>